ES6核心特性详解：解构赋值、函数参数、模块系统与Symbol类型

数组解构示例

//ES6
let [x,y]=[1,2];//x=1,y=2
//ES5
var arr=[1,2];
var x=arr[0];
var y=arr[1];

变量交换示例

let x=1,y=2;
[x,y]=[y,x];x=2 y=1

对象解构示例

let obj={x:1,y:2};
let {x,y}=obj;//a=1,b=1

let {x:a,y:b}=obj;//a=1,b=2

模拟多返回值示例

function doSomething(){
   return [1,2];
}
let [x.y]=doSomething();//x=1.y=2

参数默认值模拟示例

function doSomething({y:1,z:0}){
   console.log(y,z);
}
doSomething({y:2})

默认参数示例

function doSomething(){
   return x*y;
}
doSomething(5);//10
doSomethinf(5,undefined);//10
doSomething(5,3);//15<br><br>//ES5中给参数赋默认值<br>function doSomething(x,y){<br>y=y===undefined?2:y;<br>return x*y;<br>}

REST参数示例

funtion doSomething(x,...remaining){
  return x*rremaining.length;
}
dodSomething(5,0,0,0);//15

命名导入示例

//lib/ath.js
export function sum(x,y){
  return x+y
};
export var pi=3.14;
//app.js
import {sum,pi}form"lib/math.js";
console.log(sum(pi,pi);

通配符导入示例

//app.js
import*as math form"lib/math.js";
console.lgo(math.sum(math.pi,math.pi));

默认导入示例

//lib/my-fn.js
export default function(){
  console.log('echo echo);
}
//app.js
import doSomething from 'lib/my-fn,js';
doSomething();

类定义与实例化

class Vehicle{
   constructor(name){
     this.name=name;
     this.kind=''Vehicle";
   }
  getName(){
     return this.name;
  }
};
//Create an instance
let myVehicle=new Vehicle('rocky');

继承与super使用

class Car extends Vehicle{
   constructor(name){
      super(name);
      this.kind='car';
   }
}
let myCar=new Car('bumpy');
myCar.getName();//'bumpy';
myCar instanceof Car;//true
myCar instanceof Vehicle;//true

Symbol创建示例

const MY_CONSTANT=Symbol();
let obj={};
obj[MY_CONSTANT]=1;